1. Field of the Invention
This invention relates to methods for making smooth surfaces for microelectronic and chemical/biological assay applications. In a preferred embodiment, a gold electrode is created having a substantially molecularly smooth surface; the electrode is part of a genetic analysis chip and an oligonucleotide can be attached to the smooth surface.
2. Description of the Related Art
Many technologies use electrical circuit contacts embedded or otherwise attached to a substrate. Many of these further provide for attaching molecules, particularly complex biological molecules, to an electrical contact surface. For example, in the field of genetic analysis, strands of oligonucleotides such as DNA are commonly attached to the surface of an electrode (e.g., U.S. Pat. Nos. 5,312,527; 5,776,672; 5,972,692; 6,200,761; 6,221,586.) Other biological and nonbiological sensors and assay devices similarly utilize sensor molecules (such as enzymes or receptors) attached to an electrode.
For molecules such as DNA to attach uniformly and reliably to the surface of an electrode, it is desirable that the electrode surface be as smooth as possible, ideally, the surface would be atomically smooth.
Presently, there are several methods for making electrode surfaces by depositing a conductive layer on a substrate. For example, gold and other metals have been deposited on semiconductor substrates using methods such as evaporation, sputtering, and electroplating. Unfortunately, these methods typically create a metal layer with a top surface that is too rough for some applications. For example, an evaporated gold surface can have a roughness as high as 200 Å. This roughness on the surface can change the packing density of of DNA molecules deposited on the gold surface and significantly affect the structural integrity of DNA monolayers formed on the gold surface.
Hence, there exists a need for a method of creating very smooth surfaces on materials capable of conducting electrical current. In particular, there exists a need in the genetic analysis field and in other assay devices for a method of creating an electrode surface on a substrate where that surface is substantially molecularly smooth.